S5 Masters panning issue

[Rpro]

I have a few stereo tracks assigned to a few masters and have assigned the masters to the strips. When the pan knob is centered on the masters strips the audio is in both speakers and the control meter on the 401 shows this. When I pan the master pan knob to hard left the audio is in both speakers and the meter shows this but when I pan the master hard right the audio is on the right speaker only and the 401 meter shows this. I cannot pan the masters track audio left even though the pan knob on the 408 is panned hard left.

The stereo tracks are panned hard left and hard right. The Pan to button is lit on GRP and MIX on the 408.

Any idea what could be wrong?